1. Field of the Invention
The present invention relates generally to irrigation control devices, and more particularly to the powering of irrigation control devices using an energy reserve.
2. Discussion of the Related Art
Typical irrigation control systems cooperate with water valves and pumps to control the flow of irrigation water through a variety of water dispensing devices, including sprinklers, rotors, drip-lines, and other water delivery devices. These control systems are used in a wide variety of irrigation applications, from residential and commercial landscapes to golf course and agricultural irrigation. Rotors, for example, irrigate by throwing a jet or spray of water that is rotated about a generally vertical axis. Rotors are supplied with water from water supply lines that are usually installed below ground and are typically actuated by electric solenoid-controlled valves.
Water flow through a rotor or other water delivery device is often controlled through the use of a valve that is transitioned between open and closed states. In many instances the position of the valve is controlled by a solenoid. Two common forms of solenoids used for irrigation are latching solenoids and non-latching solenoids. A typical non-latching solenoid requires continual power to maintain the open (irrigating) position. Thus, if power is lost or removed in a typical AC or DC non-latching solenoid, the valve returns to a closed position as a failsafe.
Latching solenoids, on the other hand, require a certain amount of energy (e.g., a first energy burst) to open, and a similar amount of energy (e.g., a second energy burst) to close. The on/off pulse is usually supplied by a large capacitor acting as a local energy reserve. If power is lost soon after the latching solenoid is turned on it may not have sufficient time to recharge its energy reserve so that it may be assured that it can also close. If power is lost and the latching solenoid cannot be closed, significant turf damage can occur due to the large amount of unintended irrigation that would continuously flow until the fault is discovered and manually corrected. In applications where a latching solenoid valve is controlled using a battery or other depleteable power source, care should be taken to ensure that sufficient energy remains to close the valve once opened to avoid overwatering.